What makes a game an “IO games” isn’t just the URL; it’s the vibe and the mechanics:

Zero Barrier to Entry: You don’t need to download anything or create an account. You just go to the website, type a nickname, and hit “Play.”

The “Growth” Mechanic: Most involve starting as something small (a cell, a tank, a snake) and getting bigger/stronger by consuming pellets or defeating other players.

Massively Multiplayer: You are dropped into a room with dozens (sometimes hundreds) of real people in real-time.

Simple Graphics: They usually feature clean, minimalistic designs—think geometric shapes, neon lines, or basic 2D sprites.

Easy to Learn, Hard to Master: The controls are usually just your mouse or a few keys, but the strategy comes from outmaneuvering other humans.